Kenwood TS-430s: SSB RX with very low AF volume and S-meter stuck at S-0.

 Repair Brief – Kenwood TS-430s – bad SSB RX.

 

DISCLAIMER: the following instructions are provided only as a report of my hobby experience. In no way I am responsible of any damage you or your device can suffer by following this procedure. Lethal voltages are present in the device!! Qualified personnel only! You know what you are doing and you are proceeding at your own risk!

 

Symptoms (RX only):

• In USB and LSB low volume and no S-meter deviation.

• Strong (local) SSB station are demodulated OK and can be heard with very high volume setting. IF-Shift and RIT working OK as well as NOTCH.

• AM and CW are OK.

 

Findings:

• In USB and LSB, the ACG line (gate of Q13) stuck at 2.5V, no matter of signal strength.

• Q17 (what is it useful for?!) voltages: 2.6V all terminals as per schematics.

• SSB line goes high when USB or LSB are selected (as expected).

• On AM S-meter is well calibrated for S-0 and S-9.

• CAR signal present @305mV RMS in USB, CW (8.8314KHz) and LSB (8.8284KHz).
  It disappears in AM.
  

Signals at IF board connector 27 seem not to be OK. it seems the SSB filter is never selected, leaving the signal path open.

 

The fault:

The SSR (SSB Receive - connector 27, pin 6) signal is driven HIGH in USB or LSB. That's ok.

It is then routed to the NAR/WIDE front panel switch through the IF board connector 27. It should come back as SSW (connector 27, pin 4) with the switch in the WIDE position, or SSN (connector 27, pin 2) with the switch in the NAR position. 

 

 

Neither SSW nor SSN go high regardless of the switch position: the switch is not working or the switch board is not properly connected.

S18 found not working.

Restoring S18 solved the problem.

S18 restoration brief

You have to tear the plastic front panel down. 

Then undo the 5 screws keeping the switch unit, but do not try to extract it form the slot; just rotate it so that the switches solder joints are exposed.Ddesolder the switch you need to restore (S18, in my case).

Follow the following pics:

S18

S18 - open STEP 1

 

S18 - open STEP2

S18 down to crumbs

 

S18 detail

 

S18 detail - before cleaning

 

S18 detail - after cleaning

S18 crumbs after cleaning

I used IPA to clean and just R-10 contact cleaner to lubricate. May be it is not enough, but
not having neither the SSB nor the CW narrow filters installed, I never ever touch that switch...
So, in my case, should the problem rise again, I would short SSR to SSW at connector 27, de facto putting the switch out of the game.

Hope this help!

Ciao.